Sheet separating system, sheet handling system, method for the frictional separation and feeding of sheets

ABSTRACT

A paper separating system, based on the frictional separation and feeding of the uppermost sheet ( 13 ) from a stack ( 14 ) of sheets of paper and flat substrates over a hurdle ( 8 ) using a separating and feeding head ( 1 ) and a deflection mechanism ( 35 ) for the head ( 1 ), the head ( 1 ) and the deflection mechanism ( 35 ) having, in particular, a roller ( 7 ) and a driving means ( 4, 5, 6 ) for the roller ( 7 ) and a resetting means ( 10 ), a means ( 31, 32, 36, 37, 28, 30, 23, 27, 28 ) for definitively or temporarily stopping, delaying or slowing down the head ( 1 ) being provided in the region of a separating distance (d v , d 2 -d 1 ) between the hurdle ( 8 ) and head ( 1 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This case is a national application which claims priority of German Application No. 10 2005 056 634 filed Nov. 25, 2005.

The invention relates to a sheet separating system based on the frictional separation and feeding of the uppermost sheet from a stack of sheets, such as sheets of paper or flat substrates, over a hurdle using a separating and feeding head, a deflection mechanism and a resetting means for the head, a sheet handling system and a method for the frictional separation and feeding of the uppermost sheet from a stack of sheets, such as sheets of paper or flat substrates, over a hurdle with the sheet separating system.

Sheet separating systems of an older type are disclosed, for example, in AT 329 093 or DE 18 00 96. These systems have a lifting mechanism which is moved uniformly and positively, for example by an eccentric disk, and with which a feed slide is moved parallel to a stack of sheets on the uppermost sheet along a forcibly predefined movement contour which is always the same. At its free end the feed slide has a friction roller which is locked against rotation for movement in the feeding direction and can be rotated in the opposite direction of movement. As a result, whenever the feed slide moves to and fro uniformly, the respective uppermost sheet of the stack is fed to a copier. Such sheet separating systems are based on a concept which entails disadvantages since the separating and feeding force which acts on the uppermost sheet by means of the feed slide with a fixed friction roller is already. independent, owing to the forcibly predefined movement contour, of a resistance of the uppermost sheet, actually opposed to this force, for separating and feeding said sheet over a hurdle. Such systems cannot be set to different thicknesses of paper with in particular different flexural strengths and are not suitable for modern paper handling systems owing to the variety of problems which result from this.

An advanced sheet separating system which is mentioned at the beginning is disclosed in U.S. Pat. No. 5,377,969 and DE 199 50 307 C1, in which a freely movable and drivable frictional roller can be moved away from the hurdle in a plane parallel to the stack. In U.S. Pat. No. 5,377,969 this makes it possible to set automatically a distance between the frictional roller and the hurdle which is optimum for a specific degree of rigidity of a sheet to be separated. In DE 199 50 307 C1 a contact pressure of the roller can be increased automatically for sheets of relatively high rigidity by means of a rocker bearing.

With such improved systems there is still the problem of multiple drawing in of sheets (multipick). The main cause for multipick is that an advancing force of the separating and feeding head (feed head) which acts on the uppermost sheet of a stack of sheets of paper or flat substrates, what is referred to as a buckling force when customary, uniform deflection of the head occurs, exceeds a separating distance to such an extent that the excessive amount is sufficient not only to push the uppermost sheet but also a further sheet or a plurality of further sheets onto the hurdle, in particular transporting hurdle, counter to the buckling force-essentially a frictional, upsetting and bending force of the sheets.

Increasingly, modern paper handling systems are designed to largely avoid multipick. It would be desirable to reduce the proportion of multipicks when separating sheets of paper.

This is the point of departure for the invention whose object is to specify a sheet separating system, a sheet handling system and a method of the type mentioned at the beginning in which the proportion of multipicks during sheet separation is reduced compared to known systems.

SUMMARY OF THE INVENTION

The object is achieved by providing a sheet separating system based on the frictional separation and feeding of the uppermost sheet from a stack of sheets, such as sheets of paper or flat substrates, over a hurdle using a separating and feeding head, a deflection mechanism and a resetting means for the head, characterized in that a means is provided for stopping, delaying or slowing down the head for the region of a separating distance (d_(v), d₂-d₁) between the hurdle and head. The object is further achieved by providing a method for frictionally separating and feeding the uppermost sheet from a stack of sheets, such as sheets of paper or flat substrates, over a hurdle having a sheet separating system comprising the separating and feeding head is deflected with respect to the resetting means by means of the deflection mechanism and brings about sheet separation, characterized in that the deflection of the head is stopped, delayed or slowed down in the region of a separating distance (d_(v), d₂-d₁) between the hurdle and head.

The invention is based on the idea that an equilibrium between the buckling force and the advancing force occurs only in the region of the separating distance. The forces which oppose the advancing force are composed of the respective sum of frictional forces, upsetting forces and bending forces at the transport hurdle (buckling force) and a compressive force of the head on the stack whose size and direction are conditioned by the gravitational force of the mass of the head and an angle—dependent normal force proportion of the opposing forces acting on the paper stack.

The invention has recognized that this equilibrium is displaced surprisingly quickly in favor of the advancing force in the course of the deflection of the head over the separating distance—and this occurs owing to an increasingly reduced flexural strength of the sheet to be separated and a further increase in the normal force acting on the sheet to be separated.

In view of this, the concept of the invention proposes that a sufficient period of time is made available in which, after the separating distance between the head and hurdle has been traversed, the advancing force just exceeds the buckling force to such an extent that only a single sheet can be drawn in. The deflection of the head is preferably definitively or temporarily stopped, delayed or slowed down in the region of the separating distance, in particular compared to a deflection of the head which is usually brought about in a uniform way by driving means and resetting means. This ensures that precisely that period of time in which the advancing force exceeds the buckling force by an amount which is only sufficient to draw in one single sheet is extended in practice. Owing to the extension of the period of time, it becomes possible for the abovementioned magnitude of the advancing force, which exceeds the buckling force, both to act long enough and yet to be sufficient to draw in just a single sheet. As a result, multipick is prevented in practice.

In a first variant of the invention, the concept can be implemented in such a way that the head is stopped in the region of the separating distance. This can be realized in a particularly simple way. The location where stopping occurs can be expediently matched to the quality of the sheet to be separated.

In a second variant of the invention, deflection of the head can be delayed in the region of the separating distance by impeding the deflection, for example by means of a damping element. This has the advantage that in particular different flexural strengths of sheets can be taken into account by means of the configuration of the impeding distance or the delay period —in other words in the second variant the advantageous effect of the concept explained above can be achieved for a greater range of types of sheet than with the first variant.

In a third variant of the invention, the deflection of the head in the region of the separating distance is actively delayed. This can be done, for example, by slowing down the deflection movement of the head, for example by means of an actively slowed down driving means, in particular by means of a controller. This can be advantageously implemented as an alternative or in addition to the first or second variant of the invention.

A fourth variant of the invention provides for the distance between the head and the hurdle to be increased only successively, for example regulated by means of a controller (feed controller) if a sheet movement sensor does not signal any movement, or only insufficient movement, of the uppermost sheet. Expediently, during subsequent sheet supply sequences a distance between the head and the hurdle is increased until an acceptable ratio of the speed of the sheet to the advancing speed of the head, in particular the circumferential speed of the frictional roller, is reached, said ratio being stored by the controller. This has the advantage that such a sheet separating system sets itself to different states and sorts of sheets of paper or thin substrates automatically owing to the adjustment by the controller and the movement sensor.

Further advantageous developments of the invention can be found in the subclaims and specify in particular advantageous possible ways of realizing the concept explained above within the scope of the setting of an object, and in terms of further advantages.

Exemplary embodiments of the invention are described below with reference to the drawing in comparison with the prior art which is also presented in part. The drawing is not intended to illustrate the exemplary embodiments to scale but rather is executed in a schematic and/or slightly distorted form wherever expedient for the purposes of explanation. For supplementary information about the teachings which can be directly discerned from the drawing, reference should be made to the relevant prior art.

It is necessary to take into account here that various modifications and changes to the form and details of an embodiment can be made without departing from the general idea of the invention. The features of the invention which are disclosed in the description above, in the drawing and in the claims may be essential to the development of the invention either individually or in any desired combination. The general idea of the invention is not restricted to the precise form or detail of the embodiments which are shown and described below or restricted to a subject matter which would be restricted compared to the subject matter claimed in the claims. For specified dimensioning ranges, values which lie within the aforesaid limits should also be disclosed as limiting values and be capable of being used and claimed as desired.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the invention further, preferred embodiments of the invention relating to a paper separating system and a method for the frictional separation and feeding of the uppermost sheet from a stack of sheets of paper over a transport hurdle using a separating and feeding head (referred to below as feed head) will be explained with reference to the Figures of the drawing.

In the drawings:

FIG. 1 shows the basic principle of paper separation according to the prior art;

FIG. 2: is a schematic illustration of the system shown in FIG. 1 with the forces which usually occur during paper separation;

FIG. 2A: shows an exemplary comparison of the force profiles acting during a separating and feeding process for a compressing/bending curve of a sheet (buckling force) on the one hand and a motor driven separating force (advancing force of the separating and feeding head) on the other, plotted against the travel of a separating and feeding head relative to a hurdle;

FIG. 2B: shows an exemplary comparison of a uniform speed profile of a separating and feeding head according to the prior art (undamped curve) on the one hand and a non-uniform speed profile of a preferred separating and feeding head for a sheet separating system according to the concept of the invention (damped curve) on the other, plotted against time;

FIG. 3: shows a first embodiment of a paper separating system according to the first or second variant of the invention in which a deflection mechanism is arranged on the inner upper side of a draw in shaft;

FIG. 4: shows a damping system which can advantageously be used in the embodiments in FIGS. 3 and 7 to 13, according to the concept of the first or second variant of the invention;

FIG. 5: shows a travel/time diagram, for example for a damping system in FIG. 4 or FIG. 16 and FIG. 17, which illustrates the movement profile of a deflection of the feed head which is damped in its deflection in the region of the separating distance, according to the concept of the first or second variant of the invention;

FIG. 6 shows a travel/speed diagram according to the prescriptions in FIG. 5;

FIG. 7 to FIG. 10: show a further embodiment of a paper separating system in which a damping system according to FIG. 4 according to the concept of the first or second variant of the invention is used—FIG. 9 and FIG. 10 illustrate the comparison the embodiment without and with damping system;

FIG. 11 to FIG. 13: also show a further embodiment of a paper separating system in a side view (FIG. 11) and plan view (FIG. 12) in which a damping system according to FIG. 4 in accordance with the concept of the first or second variant of the invention is used—FIG. 13 shows a detail from FIG. 11, FIG. 12;

FIG. 14 to FIG. 17: show a further damping system which can advantageously be used in the embodiments in FIG. 3 and FIGS. 7 to 13 according to the concept of the first or second variant of the invention;

FIG. 18: shows an embodiment of a paper separating system in which, according to the third variant of the invention, the deflection of the feed head is actively slowed down by means of the drive means;

FIG. 19: shows a travel/time diagram which schematically explains the movement of the feed head in the embodiment in FIG. 18 for a less flexurally rigid sheet of paper;

FIG. 20: shows a travel/time diagram which schematically explains the movement of the feed head in the embodiment in FIG. 18 for a flexurally more rigid sheet of paper;

FIG. 21: also shows an embodiment of a paper separating-system according to the third variant of the invention;

FIG. 22: shows an embodiment of a paper separating system according to a fourth variant of the invention; in which the distance between the feed head and the transport hurdle is increased successively;

FIG. 23: shows a further embodiment according to a fourth variant of the invention in which the distance between the feed head and the transport hurdle is successively increased; and

FIG. 24 also shows a further embodiment according to the fourth variant of the invention.

DETAILED DESCRIPTION

The embodiments of the apparatus and of the method explained here are used, according to the concept of the invention, to optimize the reliability when separating stores of sheets in the form of stacks which are separated using a separating system. Identical reference symbols have been used for corresponding parts. The separating system according to the embodiment comprises essentially a frictional roller 7 which is shown in FIG. 1 and is driven by an (electric) motor and frictionally separates the uppermost sheet 13 of a stack of sheets of paper or substrates from the rest of this stack and feeds it to a pair of rollers via a mechanical ramp 8, 12 (which in addition to applying friction to the stack functions as a second hurdle).

The paper stack is usually stored in a shaft or a cartridge.

The single sheet can be drawn from the cartridge using the separating device (also referred to as feeder).

The pair 9 of rollers at the end of the ramp 8, which are also commonly referred to as exit rollers usually has a separate drive and is activated by means of a sensor 11 which is seated at the inlet of the pair of rollers. For reasons of cost or other reasons the sensor can also be dispensed with. The exit rollers are then driven continuously.

These rollers have the function of drawing the already partially separated sheet entirely from the shaft and transporting it into the following device. The subsequent paper handling system/device can be a printer, a scanner or some other device or unit which processes a single sheet. The ramp 8 constitutes here a hurdle for the paper with the function of preventing multipicks.

The cause of multipicks will be explained with reference to FIG. 1 and FIG. 2. A multipick occurs in a feed process, in particular in the described feed system, with a roller 7. The roller 7 bears against a ramp and is motor driven 4, 5, 6 counter to a spring force of a spring 10 and it runs back onto the uppermost sheet of paper 13. As the uppermost sheet 13 finally moves away, and in particular in the case of lightweight paper, the feed head 1 causes a deflection to the rear and thus brings about a position on the other side of a separating distance from the ramp 8, which is sufficient in terms of force to crush more than one sheet, bend it and thus feed it.

This gives rise to multipick in the feeder and thus to the drawing in of multiple sheets for the following device.

This can lead to problems with terminals which can only process single sheets.

This multipick is even more probable if the frictional coefficient μS₂-S₃ between the second and third sheets is lower than the value μs₁-S₂ between the first and second sheets.

This so-called “ream seam” condition is already met if the stack 14 in the paper shaft or in the cartridge is composed of a plurality of secondary stacks, which usually occurs when the cartridge is reloaded.

Separating a paper stack which is assembled by machine at the manufacturers and subsequent reassembly of said stack already results in relatively low frictional values in the junction regions of the stack 14 since the position of the sheets which are placed together by machine, and thus the relatively constant frictional coefficient with respect to one another, is virtually impossible to simulate manually but in fact is generally smaller.

If a device for removing this multipick is not installed in the downstream terminal, at least one intervention by the user is necessary to eliminate the paper jam. In an extreme case, this can require servicing, associated with a relatively long downtime of the entire system and thus incurring costs.

FIG. 2A explains, within an exemplary comparison of a buckling force and an advancing force, the recognition on which the concept of the invention is based that an equilibrium between the aforesaid forces in the profile of the deflection of the head 1 or of the roller 7 with respect to the ramp 8 is displaced beyond a separating distance si surprisingly quickly, for example to the position S₂, in favor of the advancing force—this occurs owing to a progressively decreasing flexural rigidity of the sheet to be separated (buckling force) and to a further increase in the normal force acting on the sheet to be separated (advancing force). The buckling force is represented here essentially by an exemplary compressing/bending curve of a flat substrate on the ramp 8, while the advancing force, here in the form of a motor driven separating force, rises linearly, especially owing to the resetting means in the form of a spring 10 here, i.e. here a feed head 1 is deflected away from the ramp 8 on the uppermost sheet of paper 13, counter to the force of a spring 10 secured to the housing, until the increasing stressing force of the spring 10 has reached a value which is sufficient to overcome the mechanical resistance force of the sheet of paper 13 on the ramp 8 in order to push the sheet of paper 13 up on the ramp 8. Said force corresponds essentially to the previously described compressing and bending force for the specific paper 13. Since the resistance of the sheet of paper 13 in practice decreases in the form of a 1/s curve with the distance s of the feed head 1 or of the roller 7 from the ramp 8, while the advancing force, i.e. in practice the spring force, in contrast increases linearly, the distance point s₁ of the feed head 1 or of the roller 7 from the ramp 8 for overcoming the forces for just one sheet is decisive for the effective separation since when this critical distance s₁ is exceeded the advancing force for more than one sheet—here for distances greater then S₂, is quickly reached and the risk of multipick then occurs.

With this in mind, the invention has, as illustrated by way of example in FIG. 2B, brought about a situation, within the scope of the preferred sheet separating system and the preferred method according to the concept of the invention, in which a sufficient period of time is made available for the advancing force to just exceed the buckling force—after the separating distance s₁ between the feed head 1 or roller 7 and hurdle 8 has been exceeded—that only a single sheet can be drawn in. In FIG. 2A, this is here the distance range up to S₂ which exceeds the separating distance s₁ and corresponds to the time period between t₁ and t₂ illustrated in FIG. 2B. The deflection of the head is preferably definitively or temporarily stopped, delayed or slowed down in the region of the separating distance, i.e. here in the range between s₁ and S₂. This is illustrated by way of example in FIG. 2B by the damped curve which illustrates a slowed down speed of the head 1 or of the roller 7 between the times t₁ and t₂—this is illustrated in comparison with a deflection of the head which is brought about uniformly according to the prior art explained at the beginning using drive means and resetting means and is illustrated in FIG. 2B as a non-damped curve. This is achieved by virtue of the fact that precisely that distance range S₁ to S₂ is in practice extended to a time range t₁ to t₂ in which the advancing force exceeds the buckling force by an amount which is just sufficient to draw in a single sheet. Owing to the extension of the aforesaid distance range to the aforesaid time range it becomes possible for the aforesaid amount of the advancing force which exceeds the buckling force both to act for long enough and to be sufficient to draw in just a single sheet. Multipick is thus prevented in practice.

A so-called top fixing arrangement is shown in FIG. 3. In a simple embodiment, the feed head 1 is attached via a linkage in the form of an arm 2 to the upper side of a paper shaft 3 in a suspension device 25 so as to slide in the running direction of the paper.

The feed head 1 with a drive motor 4, worm 5 which is driven by the latter and a shaft 6 which is driven by means of this worm 5 drives a frictional roller 7 when the motor is energized.

When the motor is energized, the feed head 1 with the roller 7 runs in a frictionally engaging fashion over the uppermost sheet 13 counter to the force of the spring 10 in the rearward direction until the spring force overcomes the opposing forces during the sheet separation process and the uppermost sheet 13 is separated from the rest of the stack 14.

In the process, the sheet 13 is usually pushed up on the ramp 8 where it is taken up by the extraction rollers 9.

As is apparent from FIG. 2, during the separation process the adhesion friction force of the uppermost sheet with respect to the following sheet F_(fr1−2) firstly acts and then the force F_(b1) which is necessary to compress the sheet of paper on the ramp 8, which then becomes a bending force, and in addition the sliding friction force of the underside of the uppermost sheet of paper with respect to the upper side of the following sheet and the frictional force of the separated sheet with respect to the surface material of the ramp as counter forces with respect to the spring 10.

These forces do not all act simultaneously. However, the initial force for releasing the sheet of paper is largest since here the relatively high static coefficient of friction of paper 13 to paper 14 and the high compressive force of the paper 13 on the ramp 8 coincide.

Accordingly, usually a feed head 1 which can be deflected about an axis counter to a spring 10 will firstly attempt to move out to the rear.

In the process, the mass of the feed head is speeded up to such an extent that even after a separating distance is reached with a force equilibrium position for the advancing force and buckling force—cf. FIG. 2A—the head does not stop abruptly in its movement, while the uppermost sheet 13 starts to move but rather is moved further towards the rear due to mass inertia.

As a result, the force acting on the uppermost sheet 13 is consequently sufficient even to feed a plurality of sheets of paper from the stack 14 out of the cartridge simultaneously, which is commonly referred to as multipick.

Previously known feed systems according to FIG. 1 have in common the fact that the intended increase in the distance between the feed head 1 (head) and the ramp 8 (hurdle) occurs by means of an acceleration process of an undamped spring mass system.

Owing to the given mass of the feed head 1 (approximately 80 g to 200 g) and the initially still low force of the spring 10 as well as further relatively small frictional forces during the movement of the head, this inevitably causes the range of the separating distance to be passed through at the force equilibrium point which occurs between the spring force and the force necessary to detach and move the uppermost sheet of paper as the feed head 1 moves back.

As a result, in particular in the case of thin pieces of paper which are generally less flexurally rigid, there is the probability of multipick because here the force for detaching more than one sheet is already achieved by a small increase in distance from the ramp.

The invention has recognized how the situation of such multipick can be avoided. According to the concept, the feed head which is spring mounted in the deflection direction is held for longer than usual in practice, i.e. stopped, delayed or slowed down, in other words it is temporarily stopped or its speed is temporarily limited at the distance position which is suitable for the simple separation process, i.e. in the region of the separating distance, i.e. in the region about a force equilibrium position for the advancing force and buckling force—cf. FIG. 2A—in such a way that shortly after the equilibrium position of the feed force F_(f) with the forces F_(b) which are necessary to firstly move and detach the uppermost sheet from the following sheet is reached in the region of the separation distance, the feed head 1 does not move, or at least however only moves slowly further towards the rear—cf. FIG. 2B—so that no unacceptable increase F_(f) in the feed force or any disadvantageous reduction in the flexural rigidity F_(b) occurs.

Without such a measure, in the cases according to FIGS. 1 and 2 the spring mass system is virtually undamped, which unavoidably entails, with the mass of the feed head and the acceleration from the motor, overshooting beyond the force equilibrium point, and making multipick behavior probable.

The forward force or advancing force F_(f), which in the arrangement according to FIG. 2 is the forward driving force F_(f) which firstly works counter to the frictional resistance of the piece of paper located under the feed head with respect to the following sheet of paper and then counter to the flexural rigidity of this piece of paper on the ramp and counter to the frictional force occurring there, is referred to commonly as buckling force F_(b). It constitutes a sum of forces which, when the uppermost sheet first becomes detached, are necessary to apply compression force to the ramp and for the forward movement on the ramp.

According to the concept of the invention, the feed head 1 is deflected or can be deflected only as far as such a distance which is absolutely necessary to separate a single sheet —however not to such an extent that the force is sufficient for the process of simultaneously feeding more than one sheet of paper.

This can occur in different ways in the individual feed systems. The concept comprises a plurality of variants. The individual measures for this are described below.

In this respect, a paper separating system is described with reference to the following FIG. 3 to FIG. 24, said system being based on the frictional separation and feeding of the uppermost sheet 13 from a stack 14 of sheets of paper and flat substrates over a hurdle 8 using a frictional roller 7. The latter is spring mounted 10 in the deflection direction and motor driven counter to the opposing force during the separation of the sheets of paper (reference symbols 4, 5, 6). The opposing forces are composed of the respective sum of frictional forces F_(r), compressive forces and bending forces F_(b) on the slope 8 and the contribution of a pressing force of the frictional roller 7 on the stack 14 whose magnitude and direction are conditioned by the gravitational force of the feed head mass and a deflection-dependent normal force component N of the opposing force roller on the paper stack 14, at any rate in the embodiments as in FIG. 3 and FIG. 7.

1. Basically, in order to overcome the aforesaid problems, a damping element in the return travel path impedes the motor-accelerated return travel of the feed head 1 in the embodiment according to FIG. 3 to FIG. 17 in such a way that within the damped region the feed head runs only at a constant speed and can only be accelerated again afterwards.

In the simplest case, it is possible to largely dispense with the free return travel of the feed head 1 which is only braked by spring force, and after a short distance from the ramp the feed head can be held at its distance from the ramp by means of a securing element, and cannot be deflected further.

2. In the embodiment according to FIG. 18 to FIG. 21, the motor driven distance from the ramp 8 is so slow that virtually no overshoot of the feed head 1 can occur and the sheet of paper 13 which is resting uppermost is separated from the following sheet 14 at the smallest possible distance from the ramp 8.

3. An adaptive control is achieved according to the embodiment in FIG. 22, FIG. 23 and FIG. 24. For this purpose, the distance between the ramp 8 and the feed head 1, which is initially zero or virtually zero, is increased only successively by means of the actuating element 27, 28 by the program in a feed controller 26 if the paper movement sensor 22 does not signal any movement of the uppermost sheet 13, or only signals an inadequate movement, and during the subsequent sheet supply sequences said paper movement sensor 22 increases its distance from the ramp until an acceptable ratio of the paper speed of the sheet 13 with respect to the circumferential speed of the feed roller 1 is reached, said ratio being stored in the controller program.

In particular:

Re 1. Hard Stop (Passive)

To do this, the return travel is. abruptly stopped mechanically by means of a stop after a defined return travel distance of the feed head.

This is intended to counteract unacceptably large deflection of the head 1 away from the ramp 8. While with predominantly thin, generally less flexurally rigid sheets of paper the feed process proceeds with good separating values (that is to say no multipick or only very few so-called multipicks), with relative strong substrates a no pick ratio can increasingly be found to occur, since the flexural rigidity at this short distance is too high and the roller 7 consequently rotates without adhesion over the paper 13 provided that sufficient torque is provided by the motor (the feeder operates in the slip mode).

Re 1. Damping System (Passive)

The damping element can be a mechanical damper, for example a commercially available silicone damper such as is illustrated in FIG. 4 which operates axially or radially, a pneumatic damper or an electrical or magnetic or electromagnetic damper. The electrical (for example eddy current brake principle), magnetic or electromagnetic design advantageously permits here the timing of the start, the time period and/or the damping force to be controlled by means of the respective energization. Details on magnetic or electromagnetic design are presented in FIGS. 16 and 17.

FIG. 5 and FIG. 6 each show a diagram which explains the effect of the damping system which is shown, inter alia, for FIG. 3 (top suspended feeder) in FIG. 4 as well as FIGS. 16 and 17.

While in less flexurally rigid (usually lightweight) substrates the feed process takes place near to the ramp (time period t_(v),distance range dv, in FIG. 5 the damped distance d_(v) must firstly be passed through only relatively slowly in the time period t_(v) with flexurally rigid substrates before the feed head runs again without this resistance, and thus more quickly again, towards the rear after the damping distance d_(v) has ended. The motor is firstly normally accelerated in the time period t_(b), which is followed by the damped time period t_(v). This temporary damping leads to a certain delay in the feed times in relatively thick substrates since the feed head 1 is accelerated again in the normal way (time period t₂b) only after the distances d_(b) and d_(v) have been passed through in the region of the separating distance with speed limitation. The feed position for flexurally rigid substrates is therefore reached later, which however has a minimum influence on the feed throughput rate, the so-called page/minute rate.

In the damped region t_(v), the motor speed is reduced to a lower and constant speed by means of the inter pulse period modulation (PPM) before being accelerated again after the time period t_(v) which corresponds to the run through time of the damper.

As a result, the loss of speed in the damped region is compensated again and the throughput rate is thus optimized.

FIG. 6 shows the associated diagram which represents the speed in relation to the position of the feed roller in the return travel.

In a further embodiment (delta feeder) which is shown in FIG. 7 to FIG. 10 the feed head 1 is attached to the two joints 15 by means of a suspension in the form of a lateral arm 2 in such a way that it can be moved up and down parallel to the ramp in a geometrical radius and bears with its proportional arm and head weight N on the paper (FIG. 8). The geometry of the arrangement is selected here in such a way that a stack height of approximately 60 mm is possible.

Here too, the return travel is brought about by means of a compression spring or tension spring 10. The angle a is here the angle of the ramp 8 which occurs offset again by 90° in the suspension. Of course, in this context this type of lateral suspension (FIGS. 9, 10) can be implemented on both sides.

One advantage of this embodiment is the strict parallelism of the movement of the feed head (FIG. 7) with respect to the ramp 8 when the stack height is approximately 60 mm, which corresponds to the height of a commercially available paper stack 14. The feed head 1 can be prestressed against the ramp 8 here by means of the spring 10 with a force F_(c) so that it bears with a defined force against the ramp 8. It is also possible to keep the feed head 1 at a minimum distance from the ramp.

As is apparent from FIG. 10 in conjunction with FIGS. 7 and 8, when the feed head 1 is suspended laterally it is also possible to damp the return travel on a feed arm 2 and a longer dwell time on the ramp 8 is thus possible. For this purpose, the damping element 31, 32 which is of similar design to that in FIG. 4 is attached to the arm rocker of the feed arm 2.

FIG. 9 shows the basic design as disclosed in the German application with official application number 10 2004 038 753.2, but without a damping system 31, 32. The content of the application is incorporated into the present description.

A toothed rack 32 which is temporarily placed in engagement with the teeth of the damping element 31 when the head 1 moves back is mounted on the feed head 1. The number of teeth which are engaged and their position determine the duration of the damping or the beginning.

An additional motor controller, as indicated in FIG. 15, is also possible and as with the different suspension in FIG. 15 it optimizes the feed sequence in terms of timing.

Yet a further embodiment of a paper separating system with a damping system in FIG. 4 is shown in FIGS. 11 to 13 (high capacity feeder).

For relatively high paper capacities (approximately 1000 and more sheets) a lifting base is used.

In the embodiment shown in FIG. 11, the feed head 1 is pivotably attached to a fixed arm 2 on the upper inner side of the shaft 3. As an alternative to this, it can be attached to the left-hand and/or right-hand side of the housing 3 as in FIG. 12. When there is an attachment on both sides, the arm can be laterally displaceable in order to allow the feed head to rest in the center of the sheet, on the substrate to be separated (see FIG. 12). The feed head rests here only with its proportional gravitational force N under the roller on the paper while the weight of the arm, which is permanently attached to the housing, is not included in the bearing force (FIG. 13). This embodiment is advantageous for single separation owing to the low weight at the bearing point. After a feed sequence which corresponds to a height reduction of 1 mm at maximum, the sensor 22 transmits the signal, under the control of the sensor flag 33, to the controller to interrupt the to separating process and raise the lifting table 20, for example using the servomotor 21. Together with the geometry of the arrangement of the sensor flag 33, the switching hysteresis of the sensor 19 determines the lift of the table. After the lifting process has ended, the rest of the feed sequence can be continued.

In all the explained embodiments (top suspended feeder, FIG. 3, delta feeder, FIG. 7, FIG. 10, high capacity feeder, FIGS. 11-13), the use of the abovementioned pneumatic, magnetic or electromagnetic damper is also possible.

Re 2nd Motor Controller (Active)

In another speed limiting method which does not require a mechanical damping element, the speed is reduced by means of a so-called motor ramp.

The motor is firstly accelerated in the normal way up to a time which corresponds to the start of the damped region. Then, the motor speed in the controller is reduced to a lower and constant speed by means of pulse width modulation (PWM) 30 before being increased again after the time period—which in the analogous case in FIG. 4 corresponds to the run through time of the damper. It is also possible to perform control by means of the analog change of the supply voltage here.

As a result, the speed loss in the damped region is partially compensated again and the throughput rate is thus optimized. FIG. 19 and FIG. 20 show the associated diagrams which show the distance of the feed head from the ramp in the chronological profile. With this type of improvement of the multipick rate, the motor controller brings by means of a speed setpoint curve in the feed controller (FIG. 18, FIG. 21). For this purpose, the respective angular speed of the motor is measured, for example, by means of magnetic pulses. A magnet ring 16 which is mounted on the motor axis and which has at least four poles serves here as the pulse transmitter. The angular speed and thus the circumferential speed of the feed roller 7 is determined with a so-called Hall sensor 17 which measures the pulses over a short distance from the magnet ring 16. Of course, these pulses and thus the circumferential speed of the separating roller can also be measured with other types of pulse transmitters and other sensors, for example by means of a clock wheel and an optical sensor.

From each feed start the time-point-dependent speed values of the motor are compared with the permanently stored predefined values in a table in the feed controller and the motor is adjusted by means, for example, of a symbolically illustrated change 30 in the inter pulse ratio of the supply voltage.

FIG. 19 shows the travel/time diagram of the feed head for less flexurally rigid paper.

FIG. 20 shows here the travel/time diagram of the feed head for flexurally rigid paper. Curve 18 shows the travel time curve without motor control in the two diagrams. Curve 19 shows the travel/time curve with motor control. In both diagrams, the motor is accelerated up to the time period t_(b) without limitation (FIG. 19, FIG. 20). Starting from the time period t_(b), which corresponds to a distance d₁ of the roller from the ramp which has empirically been found to be sufficient to separate the least flexurally rigid sheets of paper of a given type of paper and paper size matrix without multipick, the acceleration of the motor is reduced by changing the inter pulse ratio 30, to such an extent that the feed head passes through the critical range for multipicks for the thin, generally less flexurally rigid substrates with only a slow speed (time period t_(v) in FIG. 19 and FIG. 20).

As a result, rapid travel through the first possible separating time point in the region of the separating distance and thus an excessively high distance from the ramp during the separating process are avoided. The time for the beginning of the reduction in speed and the end of said reduction is matched to the spring mass system of the feed head and to the substrates in the paper matrix with the lowest flexural rigidities.

The separation for less flexurally rigid pieces of paper with and without reduction in speed occurs, as can be seen in FIG. 19, approximately at the same time after the time periods t₂ and t₂a. The distance between the feed head 1 and the ramp 8 during the first sheet movement, which temporarily causes the head to stop after the time period t₂ or t₂a because the sheet begins to move, is significantly smaller at the low speed with d₂ compared to d₂a with a non-reduced speed of the feed head. As a result of the short distance it is however possible to reduce the multipick rate for thin sheets of paper significantly.

Even with relatively thick substrates, as illustrated in FIG. 20, the feed head passes through the time periods t_(b) and t_(v) before moving again after the delay phase t_(v) which is likewise determined empirically, towards the rear away from the ramp 8 in an accelerated fashion until the flexural rigidity of this substrate becomes so small as a result of the distance from the ramp and the spring force attained is simultaneously of such a magnitude that even this substrate can be separated in the time period t₂a. It has been found empirically that with sheets of paper with a flexural rigidity of approximately 120 g/m² and above the risk of a multipick is much less since the increasing opposing force of the spring, which increases proportionally to the deflection of the feed head, leads to a reduction in the speed of the feed head and thus to overshooting into a feed position which permits multipick, is largely prevented. With the reduction of the accelerating force of the feed head in the vicinity of the ramp, the feed process with relatively thick substrates thus occurs somewhat later so that a certain restriction of the separating throughput rate is found to occur with relatively thick substrates.

Re 3. —Adaptive Control Of The Feed System (Active)

A spacing movement of the feed head 1 from the ramp 8 occurs here, for example, by means of a position motor 27 (FIG. 22) which, under the control of the controller, moves the feed head 1 via a transmission 28 via the arm on a toothed rack incrementally in the horizontal direction and locks it in a suitable position.

As is shown in FIG. 22 to FIG. 24, when energization of the motor M1 occurs, a sensor clock wheel 24, which is attached to the feed head, makes it possible to detect by means of a photoelectric barrier OS2 whether, and if so when, the paper 13 begins to move starting from the time when the motor is energized.

A further sensor 17 on the motor axis signals whether and how fast the motor, and thus the feed roller coupled thereto, rotates. With this sensor system it is detected, by means of a feed controller device, whether sheet separation with the currently used type of paper is successful with this distance of the.feed head from the ramp, that is to say therefore whether the sheet 13 is transported to the exit rollers 9 in a suitable time.

When the clock wheel 23 does not move when the motor is energized, attempts are made to move the feed head 1 from the ramp 8 in the direction of the end of the sheet by a short distance and the feed process is started again. This process can be repeated.

The distance value which has led to an acceptable time sequence is used again for the next sheet only if there is an acceptable ratio of the movement speed of the paper to the circumferential speed of the feed roller 7.

With this type of controller 26 it is also possible to counteract changes in the ambient conditions within certain limits. For example, during the feed sequence an electrostatic charge of the separated sheet usually occurs as well as charging of the rest of the stack in the cartridge due to sheet friction and separation.

This is due to the separation of charge and the sheet friction during the separation process. While the separated sheet 13 can be neutralized again electrostatically with relatively simple means, this is significantly more complex for the rest of the stack in the cartridge.

Therefore, if a higher feed force is necessary here to overcome the additional opposing forces, the feed head is moved successively downward again when this change occurs in order to counteract the separating forces which become larger and in order to still be able to separate the sheet. This algorithm with the adaptive and incremental change of the spring parameters is stored here with its tables in the firmware of the controller 26.

The installation of such an adaptive controller is also possible in the feed system according to FIG. 23 which is designated as a delta feeder. Here, the entire feed arm is preferably moved with its arm suspension in order to counteract an increase in the weight of the feed head (see FIG. 23). The embodiment in which the motor drive is placed on the feed head (without a sketch) is also possible.

FIG. 24 shows the principle of adaptive control which is implemented in a high capacity feeder.

To summarize, a concept is explained which relates to a sheet separating system based on the frictional separation and feeding of the uppermost sheet (13) from a stack (14) of sheets, such as sheets of paper and flat substrates, over a hurdle (8) using a separating and feeding head (1) and a deflection mechanism (35) for the head (1), the head (1) and the deflection mechanism (35) having, in particular, a roller (7) and a drive means (4, 5, 6) for the roller (7), and a resetting means (10), a means (31, 32, 36, 37, 28, 30, 23, 27, 28) being provided for definitively or temporarily stopping, delaying or slowing down the head (1) in the region of a separating distance (d_(v), d₂-d₁) between the hurdle (8) and head (1). 

1. Sheet separating system for the frictional separation and feeding of an uppermost sheet (13) from a stack (14) of sheets comprises a hurdle (8), a movable separating and feeding head (1), a deflection mechanism (35), a resetting means (10) for the head (1), and means (31, 32, 36, 37, 26, 30, 23, 27, 28) provided for stopping, delaying or slowing down the head in the region of a separating distance (d_(v), d₂-d₁) between the hurdle (8) and head (1).
 2. Sheet separating system according to claim 1, wherein the head (1) has an advancing means for a sheet, in particular in the form of a frictional roller (7) driven by a driving means (4, 5, 6).
 3. Sheet separating system according to claim 1, wherein the resetting means (10) is attached to the deflection mechanism (35).
 4. Sheet separating system according to claim 1, wherein the means (31, 32, 36, 37, 26, 30, 23, 27, 28) includes means for definitively or temporarily stopping, delaying or slowing down the head.
 5. Sheet separating system according to claim 4, wherein the means for bringing about definitive stopping comprises a stop which ends a deflection.
 6. Sheet separating system according to claim 4, wherein the means for bringing out temporary stopping or deceleration has a positioning means (27, 28) wherein the head (1) can be positioned independently of a drive means (4, 5, 6) when deflection relative to the hurdle (8) occurs.
 7. Sheet separating system according to claim 4, wherein the means for bringing about temporary deceleration comprises a one of a mechanical damper, a pneumatic damper, magnetic, electric, and electromagnetic damper, which impedes a deflection.
 8. Sheet separating system according to claim 1, wherein a controller (26) is provided which is operatively connected to the head (1) and/or the deflection mechanism (35).
 9. Sheet separating system according to claim 4, wherein the means for bringing about temporary slowing down comprises a drive means (7) which is actively slowed down by a controller (26) for deflecting the head (1).
 10. Sheet separating system according to claim 1, wherein a controller (26) is operatively connected to a sensor (23) for recording a distance between the hurdle (8) and head (1) and a movement of the uppermost sheet (13).
 11. Sheet separating system according to claim 1, wherein the head (1) is connected to the deflection mechanism (35) via a linkage (2).
 12. Sheet separating system according to claim 1, wherein the deflection mechanism (35) is arranged on an upper inner side (3) of a housing.
 13. Sheet separating system according to claim 1, wherein the deflection mechanism (35) and the head (1) are integrated into a unit.
 14. Sheet separating system according to claim 13, wherein the unit is secured to a lateral inner side of a housing and on the stack (14), by means of a suspension means.
 15. Sheet separating system according to claim 13, wherein the unit is held on an upper inner side (3) of a housing on the stack, by means of a suspension means.
 16. Sheet separating system according to claim 15, wherein the stack (14) is supported by a lifting base (20).
 17. Sheet handling system comprising a sheet separating system according to claim
 1. 18. Method for frictionally separating and feeding the uppermost sheet (13) from a stack (14) of sheets over a hurdle (8) having a sheet separating system according to claim 1, comprising the steps of deflecting the separating and feeding head (1) with respect to the resetting means (10) by means of the deflection mechanism (35) and which brings about sheet separation, and stopping, delaying or slowing down the deflection of the head (1) in the region of a separating distance (d_(v), d₂-d₁) between the hurdle (8) and head (1).
 19. Method according to claim 18, wherein the deflection is stopped, delayed or slowed down definitively or temporarily.
 20. Method according to claim 18, wherein the deflection is stopped, delayed or slowed down between the head (1) and hurdle (8) by means of a damping element.
 21. Method according to claim 20, wherein damping in the region of the separating distance causes the head (1) to be firstly deflected at a constant speed and then deflected in an accelerated fashion again.
 22. Method according to claim 18, wherein the deflection with respect to the hurdle (8) is stopped, delayed or slowed down in a motor driven fashion.
 23. Method according to claim 18, wherein the deflection causes a distance between the hurdle (8) and head (1) to be increased successively under the control of a controller (26) if a paper movement sensor (22) does not detect any movement, or only an insufficient movement, of the uppermost sheet (13).
 24. Method according to claim 18, including feeding in sheet supply sequences wherein a first sheet supply sequence a distance from the hurdle (8) is increased until an acceptable ratio, stored for a controller (26), of the speed of the paper to the advancing speed of the head (1), is reached. 